Baltimore Mayor Martin O'Malley has settled on Prince George's County Del. Anthony G. Brown as his running mate in next year's race for governor and is likely to formally announce the selection Monday, said a source familiar with the mayor's plans.

O'Malley (D) said yesterday that he is close to making an offer to a lieutenant governor candidate, whom he did not name. But during an interview, O'Malley offered effusive praise for Brown, 44, a Harvard-educated lawyer and Army Reservist who recently returned from duty in Iraq.

"It would be an exciting team," O'Malley said of a pairing with Brown. "One of us has an administrative background, and one of us has a policy background. . . . It would be a really exciting opportunity for our state."

Brown, who is black and a second-term legislator from Mitchellville serving as majority whip in the House, would also add racial and geographic diversity to the ticket. Prince George's is home to more Democratic voters than any other jurisdiction in Maryland